The present invention relates to a developing solution for positive-working photoresist or, more particularly, to a developing solution suitable for use in patterning of a quinone diazide-based positive-working photoresist. The developing solution is imparted with wettability of the surface of the photoresist layer and dissolving selectivity between the exposed areas and unexposed areas improved so much that no defects are caused in the developed pattern of the photoresist layer. Further, development with the developing solution can be performed with little temperature dependency of dissolution in the exposed areas of the photoresist layer and with few drawbacks due to foaming.
In the conventional procedures for the manufacture of semiconductor IC devices, photomasks for the manufacture of ICs, printed circuit boards and the like, the substrate plate is subjected to a selective treatment before etching, diffusion and other treatment. With an object to selectively protect certain areas of the substrate surface which should be left intact by the treatment in this case, it is usually undertaken that a coating film is formed on the substrate surface with a composition sensitive to actinic rays such as ultraviolet light, X-rays, electron beams and the like, which is called a photoresist, followed by pattern-wise exposure of the coating film to the actinic rays and development to form a patterned photoresist layer.
Photoresist compositions are classified into positive-working and negative-working ones depending on the change in the solubility behavior by the exposure to actinic rays. Namely, the positive-working photoresist is imparted with increased solubility in a developing solution in the exposed areas and remains insoluble in the unexposed areas while the negative-working photoresist behaves inversely. Typical positive-working photoresist compositions currently on use include combinations of an alkali-soluble novolac resin as the base ingredient and a naphthoquinone diazide compound as a photosensitizer. While such a naphthoquinone diazide-based positive-working photoresist can be developed with an alkaline aqueous solution as the developing solution, alkaline aqueous solutions containing metal ions are undesirable as a developing solution in the manufacture of semiconductor devices because the metal ions may adversely influence the performance of the semiconductor devices processed by the development therewith. Accordingly, developing solutions containing no metal ions should be used in such a case as exemplified by an aqueous solution of tetramethyl ammonium hydroxide disclosed in IBM Technical Disclosure Bulletin, volume 13, No. 7, page 2009 (1970) and an aqueous solution of choline disclosed in U.S. Pat. No. 4,239,661.
The apparatuses of development currently used in the manufacture of integrated circuits are mostly designed for performing stationary development in order to facilitate automatization of the photoresist processing in which a developing solution is dripped and spread on the surface of a semiconductor silicon wafer coated with a layer of a photoresist composition and, after standing as such for a while, the developing solution is dripped again so that the whole process of development proceeds with the wafer kept stationary throughout. In such a process of stationary development, the spreading velocity of the developing solution over the whole surface of the wafer is the key factor which is determinant of the uniformity of the photoresist layer on the wafer surface. This problem of spreadability of the developing solution over the wafer surface is more important when the silicon wafer has a larger and larger diameter so that the wettability of the developing solution is one of the most important characteristics required of the solution.
In this regard of improving the wettability for a developing solution, it is a known and industrially practiced method that the developing solution is admixed with a surface active agent as is disclosed in Japanese Patent Kokai 58-57128. This method of adding a surface active agent to the developing solution, however, is not quite satisfactory because foams are sometimes formed on the developing solution admixed with a surface active agent which may cause defects in the patterned photoresist layer after development. Although foaming of the solution can be prevented by the addition of a defoaming agent, highly effective defoaming agents such as silicone-based ones cannot be used because they are sometimes responsible for defective development. When a developing solution for positive-working photoresist compositions is admixed with a surface active agent, in particular, a serious problem is caused in that the temperature dependency of development is increased with enhanced sensitivity at an increased temperature and reduction of film thickness in the unexposed areas.
Besides, one of the important characteristics required of a developing solution for positive-working photoresist compositions is the so-called dissolving selectivity that dissolution of the photoresist layer is complete in the exposed areas while the photoresist layer in the unexposed areas should be left intact by the developing solution with an as small as possible change in the film thickness by the development. According to the disclosure in Japanese Patent Kokai 58-9143 and 58-150949, improvements in this regard can be obtained by the addition of a surface active agent of a quaternary ammonium type or a quaternary ammonium salt, respectively. Further, Japanese Patent Kokai No. 60-12547 teaches that contrast of a positive-working photoresist composition can be increased when it is developed using a developing solution containing an alkali metal-containing basic compound and a fluorinecontaining surface active agent in combination. This method, however, is far from industrial practicability in the manufacture of semiconductor-based integrated circuits because alkali metal compounds ar detrimental to the performance of semiconductor devices in addition to the problem that patterned photoresist layers with reliability can hardly be obtained due to the increased temperature dependency in the power of the developing solution.